In the United States alone, there are approximately 40 million women who have entered their post-menopausal years. The life expectancy of a woman who attains her last menstrual period is about 28 years. A recent study indicates that 75 to 85% of these post-menopausal women will develop symptoms of estrogen deficiency. C. Hammond, M.D., et al., "Current Status of Estrogen Therapy for the Menopause," Fertil. Steril., 37(1): 5-25 (1982).
A common complaint of patients following ovarian failure is the "hot flash" or vasomotor symptom complex. This is described as a sudden onset of warmth in the face and neck, often progressing to the chest. It generally lasts several minutes, and is often evidenced by a visible red flush. These episodes may be uncomfortable. They are often accompanied by dizziness, nausea, headaches, palpitations and diaphoresis. Estrogen supplementation provides relief to over 90% of such patients.
Progressive atrophy of the genitourinary system commonly accompanies old age. It is related both to estrogen deprivation and to aging. The vagina, cervix, corpus uteri, fallopian tubes, urethra and bladder trigone all have large numbers of estrogen receptors and are sensitive to decreases in estrogen. The vagina exhibits atrophic changes from estrogen deprivation such as thinning of the epithelium, loss of rugation and a reduction in lubrication during sexual intercourse. Atrophic vaginitis accounts for approximately 15% of postmenopausal bleeding. It also contributes significantly to dyspareunia.
Atrophy of the urethra often accompanies similar changes in the vagina. Urethral atrophy often causes dysuria, frequent urination and urinary urgency. Systemic or intravaginal estrogen administration reverses this atrophy.
The most serious of all postmenopausal complications is osteoporosis. In women over 60 years of age, 25% have documented spinal compression fractures as a result of osteoporosis. As many as 50% of women will have developed vertebral fractures by age 75. The risk of hip fractures increases with age, reaching 20% by age 90. Eighty percent (80%) of hip fractures are felt to be related to pre-existing osteoporosis. Even more devastating is the fact that approximately one-sixth of women with hip fractures die within three months following their fracture. A Mayo Clinic study calculates the health care costs of fracture hospital stays at over $1,000,000,000 per year. J. Gallagher, et al., "Epidemiology of Fractures of the Proximal Femur in Rochester, Minn.," Clin. Ortho. 150: 163-171 (1980).
Although osteoporosis is relatively common in postmenopausal women, it can also occur in other estrogen deficient women and in males, in particular, in senile males. As is true for postmenopausal women, fractures associated with osteoporosis are a major problem for anyone suffering from it.
Current theories of the causes of postmenopausal osteoporosis include dietary factors and calcium intake, aging, genetic susceptibility, and Vitamin D levels. Theories of the hormonal control of bone deposition and absorption include roles for estrogen, androgens, parathyroid hormones, growth hormones and calcitonin. Current treatment for postmenopausal osteoporosis include fluoride, Vitamin D and calcium supplementation, increased physical activity and, as the primary choice, estrogen replacement therapy. The precise mechanism of the action of estrogen on bone metabolism is unknown. There are no estrogen receptors which have been identified in bone, and estrogen does not appear to stimulate osteoblastic activity. Estrogen therapy does not replace bone which has already been lost, and if discontinued, more rapid bone loss results.
Because of the potential severity and the frequency of postmenopausal complications, long-term estrogen replacement is a common practice. However, estrogen therapy has been implicated in a variety of disorders. The Boston Collaborative Drug Surveillance Program indicated a summary risk ratio for gall bladder disease in postmenopausal women taking estrogen of 2.5. Boston Collab. Drug Surv., "Surgically Confirmed Gallbladder Disease, Venous Thromboembolism, and Breast Tumors in Relation to Postmenopausal Estrogen Therapy." N. Eng. J. Med. 290: 15-19 (1974). Other studies have associated estrogen replacement with hypertension, abnormal glucose tolerance, hypercoagulability and arteriosclerosis, although these observations have not been confirmed. M. Crane, et al., "Hypertension, Oral Contraceptive Agents, and Conjugated Estrogens," Ann. Int. Med. 74(1): 13-21 (1971); R. Pfeffer, "Estrogen Use, Hypertension and Stroke in Postmenopausal Women," J. Chron. Dis. 31: 389-398 (1978); M. Notelovitz, "Metabolic Effect of Conjugated Oestrogens (USP) on Glucose Tolerance," So. African Med. J. 48(4): 2599-2603 (1974); J. Stangel, et al., "The Effect of Conjugated Estrogens on Coagulability in Menopausal Women," Obstet. Gynecol. 49(3): 314-316 (1977); T. Gordon, et al., "Menopause and Coronary Heart Disease," Ann. Int. Med. 89(2): 157-161 (1978).
Estrogen has also been suggested as a cause of benign breast disease. Estrogen receptors are known to be present in the breast. Estrogen may induce cystic or dysplastic changes in postmenopausal women, as demonstrated by mammography. Estrogen can also induce mammary tumors in animals, particularly in susceptible strains of mice and rats. Some breast cancers in women respond positively to oophorectomy, suggesting that estrogen may cause stimulation and maintenance of breast neoplasia.
Unopposed estrogenic stimulation has also been implicated in endometrial hyperplasia and endometrial carcinoma. Regular progestin administration appears to protect against endometrial cancer. However, postmenopausal women treated with estrogen-progestin combinations frequently experience regular and undesirable uterine bleeding. Thus, an alternative to estrogen therapy would be highly desirable.
There have been efforts to counteract the ill effects of estrogen therapy; for example, estrogen administration coupled with short periods of antiestrogen administration. See. A. Kauppila, et al., "Comparison of Megestrol Acetate and Clomiphene Citrate as Supplemental Medication in Postmenopausal Oestrogen Replacement Therapy,": Arch. Gynecol. 234: 49-58 (1983). In his study, Kauppila administered 1.25 mg/day conjugated oestrogens to postmenopausal women for 20 days. This was followed by a pause of 10 days. During every third pause, 10 mg of megestrol acetate was administered to one group and 50 mg of clomiphene citrate, U.S. Pat. No. 2,914,563, was administered to another group, daily for 10 days. See also U.S. Pat. Nos. 4,061,733; 2,914,562; 2,914,564; and 3,634,517. Similar tests, using conjugated estrogens with periods of clomiphene citrate administration, were reported by A. Kauppila, M.D., et al., "Postmenopausal Hormone Replacement Therapy With Estrogen Periodically Supplemented With Antiestrogen," Am. J. Obstet. Gynecol. 140(7): 787-792 (1981). See also A. J. Wise, et al., "Quantitative Relationships of the Pituitary-Gonadal Axis in Postmenopausal Women," J. Lab. Clin. Med., 81(1): 28-36 (1973). In the Kauppila studies estrogen was used as the essence of the treatment and the antiestrogen(s) were to counteract estrogen's adverse effects.
Antigonadotropic agents substantially free of estrogenic effects have also been discovered. See, e.g., U.S. Pat. Nos. 3,843,727 and 3,697,581. However, these agents are not "true" antiestrogens inasmuch as they lack estrogenic effects.
It has been observed that some antiestrogens have estrogenic effects (the so-called "true" antiestrogens). See e.g., E. Su-Rong Huang & W. Miller, "Estrogenic and Antiestrogenic Effects of Enclomiphene and Zuclomiphene on Gonadotropin Secretion by Ovine Pituitary Cells in Culture," Endocrinology 112(2): 442-448 (1983); A. Mukku, et al., "Stimulatory and Inhibitory Effects of Estrogen and Antiestrogen on Uterine Cell Division," Endocrinology 109(4): 1005-10 (1981); M. Sankaran and M. Prasad, "A Critique on the Evaluation and Mode of Action of Antiestrogens," Hormones and Antagonists Gynec. Invest. 3: 143-47 (1972); L. Terenius and I. Ljungkvist, "Aspects on the Mode of Action of Antiestrogens and Antiprogestogens," Hormones and Antagonists. Gynec. Invest. 3: 96-107 (1972); C. Geynet, et al., "Estrogens and Antiestrogens," Hormones and Antagonists. Gynec. Invest. 3: 2-29 (1972); J. Wood, et al., "Estrogenic and Antiestrogenic Effects of Clomiphene, MER-25 and CN-55, 945-27 on the Rat Uterus and Vagina," Endocrinol. 82: 69-74 (1968); K. Schulz et al., "Studies on Anti-Oestrogenic and Oestrogen-Like Action of Clomiphene Citrate--Animal Experiments," Hormones and Antagonists. Gynec. Invest. 3: 135-141 (1972); J. Clark and B. Markaverich, "The Agonistic-Antagonistic Properties of Clomiphene: A Review," Pharmac. Ther. 15: 467-519 (1982). See also, M. Pugeat, et al., "On Testing The Threshold of Sensitivity of the Gonadostat in the Late Menopausal Period: Effect of the Administration of Clomiphene Citrate or Ethynylestradiol on Plasma Levels of Gonadotropin, Testosterone and Delta-4 Androstendione," Eur. J. Obstet. Gynecol. Reprod. Biol. 9(3): 218-219 (1979); M. Zambrano, et al., "Evaluation of the Action of Clomiphene Citrate (Clomid) on Mouse Chromosomes by the Metaphase and Micronucleus Tests," Rev. Brasil. Genet. 2: 339-344 (1982); J. Gennes, et al., "Clinical, Biological, Histological and Genetic Studies of De Morsier's Syndrome (Hypogonadotrophic Hypogonadism With Anosmia)," Ann. Endrocrinol. 31(5): 841-861 (1970); I. Spitz, et al., "The Decreased Basal and Stimulated Prolactin Levels in Isolated Gonadotrophin Deficiency: A Consequence of the Low Oestrogen State," Clinical Endocrinology 16: 423-432 (1982); S. Aksel, M.D., and G. Jones, M.D., "Etiology and Treatment of Dysfunctional Uterine Bleeding," J. Obstet. and Gynec. 44(1): 1-13 (1974); T. Hashimoto, M.D., et al., "Endocrinological Study of Patients With Meningitis Tuberculosa," Jap. J. Med. 20(1): 45-49 (1981); and, C. March, M.D., "Effect of Pretreatment with Clomiphene Citrate Upon Human Menopausal Gonadotropin Therapy for Anovulation," Fertil. Steril. 26(2): 191-192 (1975). But the relevant studies have focused on the effects of antiestrogen administration on gonadotropins, rather than the effect of treatment of menopausal symptoms. See, e.g., T. Nencioni, et al., "Plasma FSH, LH and Prolactin Levels in Postmenopausal Women Undergoing Cyclofenil [sic.] Treatment," Acta Obstet, Gynecol. Scand. 61: 487-90 (1982); R. Young, et al., "Antiestrogen Effects on Gonadotropins and Uterus in the Ovariectomized Rat," Abstracts of the Endocrine Society #142, p. 108 (1979); M. Pugeat, et al., "Effects of Clomiphene and Estrogens on Circulating Gonadotropins, Testosterone, Androstenedione, in Old Menopausal Women," Ann. Endocrinol. 38: 363-65 (1977); T. Hashimoto et al., "Dual Effect of Clomiphene Citrate on Pituitary Gonadotropin Secretion in Postmenopausal Women," Endocrinol. Jap. 23(2): 115-18 (1976). One group has also studied the effects of the antiestrogen clomiphene on total body calcium in rats. A. LeBlanc, et al., "Effects of Clomiphene on Total Body Calcium in Aged Oophorectomized Rats," Calcium, Calcium Hormones, Abstract #7738, p. 1594 (1982). In fact, in an article reviewing all studies to that date on the antiestrogen clomiphene, its use in treatment of menopausal symptoms was expressly contra-indicated. J. Clark, et al., "The Agonistic-Antagonistic Properties of Clomiphene: A Review," Pharmac. Ther. 15: 467-519 (1982).
In conclusion, no one has taught or suggested use of antiestrogens to treat menopausal symptoms or osteoporosis.